Furniture drive units of this kind are known in many versions for adjusting different pieces of furniture. The drive units move parts of the furniture, such as backs, seats, mattress angles and the like. Their adjustment functions are triggered by operating switching elements on a manual control unit. When the switching element concerned is released, the adjustment function is interrupted again.
Especially in the case of furniture in the nursing and hospital sectors, it is of great importance that adjustment functions may only be triggered by authorised persons, e.g. the nursing staff. In many cases, a person lying in a bed, for example, is not supposed to perform any adjustment at all. For this purpose, various blocking systems are known, such as key switches and, for instance, rotary switches in separate lock or supervisor boxes, which are located out of the reach of a patient.
From DE 94 04 382 it is known to use magnetic key and/or touch codes, chip cards and the like, together with an additional switching means which needs to accompany it.
One disadvantage that has become apparent here is that these are only single-stage blocking devices. Since, in the course of the further development of the products, the range of their functions has also expanded considerably, it is necessary to subdivide the functions into a number of hierarchies, for which the limited functionality of the known blocking devices is disadvantageous.
A further disadvantage consists in the fact that the visual display elements are not assigned to the release elements, but only to the outputs of the control logic. Any defect in a release element is not signalled to the operator.
The invention is therefore based on the problem of developing a blocking device for manual control units for electromotive furniture drive units which breaks down the available functions into hierarchical levels that can be selected individually. In the process, the visual display should be provided with circuitry such that any defect in a release element is immediately displayed to the operator. As an additional safety means, it should also be ensured that certain functions are deactivated once a predetermined time has passed.